2PCK-Insert For Baseball Style Bump Cap - BLUE-One-Size 2 PACK! 2PCK-Insert For Baseball Style Bump Cap - BLUE-One-Size Polyethylene (PE) Shell Cap Insert encircles top, front and both sides of head to protect against bumps and scrapes Secures easily in our Vulcan Baseball Caps, or any high brow ball cap. Includes corresponding holes for cooling ventilation and foam padding against head to enhance comfort.